


Cmon This Is My Adventure

by theycallme_ook



Series: the minute you hit water [3]
Category: Batman - All Media Types, Batman Beyond
Genre: Alternate Universe - Merpeople, Batfamily (DCU), Family Fluff, Gen, Matt is autistic, becoming mer is a challenging sensory experience but its ok bc Matt's family is here for him, i hope i wrote him well to that effect, parenting books dont mention what to do when ur kids become mer, this is not a problem Mary ever thought she'd have to deal w
Language: English
Status: Completed
Published: 2021-02-18
Updated: 2021-02-18
Packaged: 2021-03-14 09:55:47
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,519
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29540616
Author URL: https://archiveofourown.org/users/theycallme_ook/pseuds/theycallme_ook
Summary: Mary McGinnis, for almost seventeen years, thought she had two human sons. Then, she thought she had one human and one half-mer son. Turns out she has two mer sons and no fully human children at all.She doesn't remember any chapter covering this in those child development books.
Relationships: Mary McGinnis & Matt McGinnis, Stephanie Brown/Tim Drake, Terry McGinnis & Matt McGinnis
Series: the minute you hit water [3]
Series URL: https://archiveofourown.org/series/2144235
Kudos: 13





	Cmon This Is My Adventure

**Author's Note:**

> poor mary has a lot thrust on her at once. she's doing her best tho and I love her

It was a typical Tuesday evening. The sun had set, the crickets were chirping, Stephanie and Timothy Drake-Brown were sitting in the lab of the cave. Both of them looking at the results of a blood test that was decidedly un-typical in confusion and unrest. Their already weird day had just gotten a bit weirder. 

“But like, how?  _ How _ did this even happen?” said Steph.

“I don’t know.” replied Tim.

“Didn’t they only go in for treatment just that once?”

“Yes. I think Mary said they didn’t even plan on having Matt.”

“And there were no more shady guys at the clinic after Terry was born, right?”

“Uh-huh.”

“Then how?”

“I dunno.”

“This is insane.”

“I know.”

They lapsed back into silence for a moment before Steph spoke again.

“So… who’s gonna tell him?”

\--

What had happened was this: Terry had been captured as the Bat Mer and locked away in an aquarium for two months. His little brother Matt had been the one to break him out. A disorientated and half feral Terry had ended up bringing both Matt and his mother to the Batcave, thus revealing the big secret he had kept from them for two years. A couple of weeks later, after Terry’s return was celebrated and dealt with, Matt and Mary had been visiting the cave. Things had been going swimmingly until Matt had asked to wear Terry’s (casual, non-Bat) pendant. Thinking little of it, Terry had agreed, and not a minute later was faced with his nine year old brother trilling up at him in confusion from the floor. His brother who now had a black and white tail. And gills. And fins.

“...mooom?”

“Yes, Terry? What is it?”

Terry made a face at the adults and a hand wave toward Matt that he hoped conveyed his desperation. Those gathered in the cave seemed perplexed for a second until they looked down and saw Matt.

Terry saw his mom's face go white as the white parts of Matt’s tail.

“Oh  _ shi- _ ”

The next few minutes were a riot of confusion on all sides. Mary, who had just discovered her second son was also a mer. Barbara, who had been  _ sure _ that C.A.D.M.U.S. (the organization they had found responsible for messing with the McGinnis couple’s fertility treatment) had combined Bruce’s DNA with Mary’s egg and thus would only make Terry half mer. Matt, who was now in a completely foreign form. And everyone else, who were just in general panic.

Terry had enough presence of mind to kneel down and scoop his little brother up in his arms when the boy started crying. He even managed to gently slip his pendant off Matt’s neck and return him to human form. Matt kept crying, but Terry knew it was probably because everyone was freaking out rather than Matt himself being hurt or anything.

“Don’t worry Matty, they’re not mad. No one’s mad. We’re just surprised, is all.”

Matt only sniffled and pressed his face further into Terry’s shirt.

“I’m sorry I yelled. I’m sorry everyone else yelled too. Do you want mom?”

Matt shrugged.

“Do you want to go upstairs? Get out of the cave for a bit?”

Matt nodded.

“Ok. We’ll go upstairs.” soothed Terry, lifting Matt up with him when he stood. He made eye contact with his mom as he did, motioning toward the stairs connecting the cave to the manor with his chin. She nodded her acquiescence and motioned that she would join them in a bit. Once upstairs, Terry set Matt down on the living room couch and slipped his jacket off to cover Matt with. Not that there weren’t any blankets, there were, Terry just hoped that something with a familiar smell and texture would help comfort Matt. Terry was moving around the room pulling curtains closed to reduce the light level when his mom and Mrs. Stephanie tiptoed in, his mom going to sit next to Matt while Mrs. Stephanie shut the final curtain. 

“You okay, baby?” Mary asked softly, holding a hand out for Matt to grab if he felt up to it. He did, evidently, because he grabbed her hand and placed it on his head, which Mary knew to be permission to start running her fingers through his hair.

“Did we scare you back there? Did I scare you? I’m sorry if I did, sweetheart.”

Matt shrugged.

“Well, you sure scared me, kid. Scared the heck out of your mom and brother, too.” said Stephanie with a conspiratorial smile, crouching down to be in Matt’s line of sight from his spot curled up on his side. “No one was expecting you crazy McGinnis’ kids to  _ both _ be merfolk. Do you know how shocked we were when your brother turned up and just ‘ _ poof! _ ’ right into a mer?”

“Yeah Matty, you should’ve seen them. I think Mr. Damian nearly im _ plo _ ded he was so shocked.”

The “imploded” comment earned him a small glare, but Terry was more than willing to drag up that stupid old argument if it took Matt’s mind off things.

“Touchy?” he asked, making a little ‘grabby hands’ motion after he’d settled down on Matt’s other side- close but not too close to crowd him. Matt shook his head no, though, so Terry kept his hands to himself.

They spent the next few minutes in silence letting Matt decompress, which Terry of all people knew he sorely needed.

“You know,” began Terry after Matt had become comfortable enough to take his hand. “I was pretty freaked out the first time I transformed too.” The kid didn’t say anything, but he did glance at Terry, so he knew he was listening.

“I guess I finally get to tell you guys this story. Pretty schway, huh? I actually found this place the night before dad died. I went to that party and ran into those Jokerz, if you guys remember. I led them all the way out here and Mr. Wayne scared them off, but then he got struck by lightning and I came up to the manor to find help. Then I found a bat stuck in the clock door and discovered the cave while trying to free it. In the cave were the pendants, and I got ahold of one, then the next thing I know I’m on the riverside by dad’s old place. It was really scary and at first I couldn’t even remember what had happened, but I remembered pretty quick how  _ weird _ it feels. Your whole body’s just  _ shifting around. _ New stuff is being added and some of your normal stuff is gone and you have all these weird new senses. I felt really confused and scared, is that how you feel, Matty?”

Matt squeezed his hand ‘yes’.

“That’s okay. It took me ages to even  _ start _ to get used to it.”

“And now you have to get used to being human again.” mumbled Matt, voice muffled even further by the jacket he had pulled up to his eyes.

“And now I have to get used to being human again.” repeated Terry, beaming. “All thanks to you, big guy. You’re the Bat Mer’s hero.”

Matt’s eyes scrunched in a way Terry could tell meant he was smiling at the reminder.

“I bet if you’re strong enough to save the Bat Mer then you’re definitely strong enough to figure out this freaky mer stuff.” said Stephanie with a grin, getting up and moving to the door. “I’ll be back with some water for you guys, but after that I’ll leave you all alone. You can call if you need anything, but take as much time as you want. Especially you, okay Matt?”

Matt squeezed Terry’s hand again and he relayed the message, at which Stephanie nodded and slipped out of the room. She returned a couple minutes later with a pitcher of water, cups and a few small snacks, setting them down on the coffee table and checking with Mary before exiting once again, leaving the small family to simply relax in each other’s presence. This was going to be quite an adjustment, dealing with both her sons being a different species, but with the Wayne pod supporting them, Mary had faith that they would all be okay.

\--

After dinner that night, which the Waynes had taken in the cave so as to let the McGinnis’s eat separately and have their space, Mary found Stephanie and Tim sitting in the lab, looking over a computer screen. They looked up at the sound of her approach, both of them shooting her smiles that were an odd mix of greeting and reluctant.

“Hey, Mary. How are the boys?” said Tim.

“Doing good. Matt’s still non-verbal at the moment but otherwise he’s fine. They’re upstairs watching a movie.”

“That’s good.”

“Yeah.”

Mary shifted to look at the computer. On it was what appeared to be the results of the DNA test Stephanie had collected Matt’s spit for earlier that evening. Mary was plenty smart, but she worked in astrotech, not biology, so the images on the screen didn’t mean much to her. The word “match” however, displayed in neat eleven point font, did.

“You know who his biological father is?”

“Yes. The same as Terry’s- though that both answers questions and raises more.”

“I thought you said Terry was mer because of a switch up at the clinic?”

“We thought so too, but that doesn’t explain Matt, so we’re looking into the C.A.D.M.U.S. folks behind it again. Trying to find someone who can give us some straight answers.” said Stephanie.

Mary nodded in acknowledgment.

“Does Terry know?” she asked once some of the dryness in her throat had receded. “Does he know Bruce is his father?”

“Maybe.” said Tim. “He declined to know when we first figured it out and it hasn’t really come up again till now, but there’s only so many orca mers out there. I wouldn’t be surprised if he’s made the connection.”

“Do you want to tell Matt?” asked Stephanie. “I mean, he’s got a right to know, and Bruce really only wanted this test done as confirmation. He’s more than willing to provide whatever support you guys need.”

The clear respect they had for her sons made Mary smile. Terry had mentioned this being like the premise of that show he liked, but Mary was certainly glad their unwitting relatives were much nicer than the children in the story had.

“I think I’ll ask both the boys if they want to know tomorrow.” she said.

“That’s good.” said Tim, exchanging small smiles with his wife. “Take it at a pace that works for them.”

“And you.” said Stephanie. “I can hardly imagine how wild this must be for you, Mary. You deserve like, a you day, or something. A treat to yourself for dealing with all the bull some super secret behind the scenes organization has put you through.”

“Oh,  _ definitely _ .” Mary laughed. “I can’t even tell my friends about this and it’s been driving me crazy.”

“That’s a yikes for sure. You absolutely need that treat. How does a trip to Atlantis sound?” asked Stephanie. Mary just stared at the other woman and hoped that her helpless expression conveyed enough.

“Ok, yeah, that might be a bit much. How about a massage day? I’ll double check that the salon is secret organization free. We can go together if you want someone in the know to talk to, or Bruce could pay for you to go with your friends. Or both- you can think of it as late child support.”

Mary chuckled. “I might have to take you up on that. Free massages sound devine.”

“It’s the least we could do, really.” insisted Tim. “You’ve done a wonderful job raising your boys. Gotham couldn’t ask for a better hero than Terry McGinnis.”

“Thank you.” said Mary, choking up a little at the reminder of her eldest’s career choice. She had mostly gotten over the initial shock, but it was still just so… new. And raw. The thought of her little baby boy going out and helping people the way he did. It terrified her, but also made her insanely proud to see him exceed the cautious hopes both she and Warren had had for him after their divorce. She and Warren might not have had the relationship they once had, but she knew Warren would be as overjoyed as she to see the man Terry was choosing to become.

“We’re the ones who should be thanking  _ you _ for not killing us the minute you found out the kinda dangerous stunts we let your son pull. Seriously, I wouldn’t blame you.” said Tim bashfully.

“Oh, don’t tempt me. I’m still thinking about it.” said Mary with a glare and a small smirk.

“So  _ that’s _ where he gets that look from.” muttered Stephanie, then following it up with a smug grin. “I always thought his smirk looked different than the boss man’s. Ter’s lucky he got his lips from his mom’s side.”

They laughed, and Mary was once again struck by the thought that things would be okay. With a family like this at their side, she and her boys would be okay. And that was all she could ask for.

\--

Mary learned to calm her racing heart a little better each day. Learned to let go of the anxiety caused by her son’s disappearance and live with the anxiety of him being the Bat Mer. Learned to manage her worry over being able to properly care for her mer sons. Learned to support them as their lives took a turn vastly different than she had ever envisioned. Learned to be okay. Learned to be.

She took Stephanie up on that massage retreat, she started taking Matt to the Wayne manor at least once a week to give him that connection he needed to this new part of his life, she used text-to-speech software to blow through all the reading material on mer the Waynes had- because though her late ex-husband may have been the marine biologist, she was still a scientist and a mother who would  _ not _ be caught unawares when her sons needed her most. It was more than a little terrifying, to suddenly realize she knew so little about her own children, but she wouldn’t take back that night at the harbor beach for anything. If nothing else, the sheer relief she could tell Terry felt made it worth the trouble. No more excuses for why he was out late, no more sneaking in at who knows when, no more cover ups or lies. He still kept secrets, of course, Mary understood there were certain things he couldn’t discuss for the sake of their safety, but she could also see that it took a weight off his shoulders not to have to hide any longer, and it made her glad. If her son was going to be out there saving the city every other week, the least he deserved was a safe and welcoming home to return to.

She didn’t usually get into such reminiscent tangents, but watching Matt splash around the cave waters on one of their weekly visits a few months after his first transformation seemed to have put her in the mood. He was so comfortable in his skin, now. It was amazing to watch the way he cut through the water with such grace. Whether he was chasing Terry around through the depths, playing with his beloved SunBoy or shadowing one of the older members of his pod ( _ their _ pod. They were a part of a pod now, her and her boys. Accepted without question by Bruce and his family) he seemed happy. Content in a way that he hadn’t been since before Warren’s murder. Overall, finding out they were mer seemed to be a catalyst for good in both her boy’s lives.

Mary shook herself out of her musings to focus on getting her wetsuit on. She had taken Stephanie up when the other woman had offered her swim gear and lessons that would allow her to (at least in part) keep up with her boys in their new world, and had come to really enjoy the time she spent in the water each week. Usually she would stay near the surface and play with Matt, but once or twice she had thrown on an oxygen tank and visited the underwater caves that the Waynes had made their home. She was getting better at scubaing, and she knew that someday soon her boys wanted to take her out for a longer dive and show her the area around the bluff; it was something she was definitely looking forward to.

Wetsuit finally zipped up and snorkel in hand, Mary made her way to the sloped stone path that led down into the water, walking in until she was shoulder deep before taking the full plunge. She opened her eyes underwater (another thing she had been practicing) and was greeted by the smiling face of her youngest son.

“ _ Hi mom! _ ” he clicked out in Jersey mer. She didn’t know much, but she had learned to recognize those two words.

“Hi baby.” she replied in English with a wave, even though the water distorted her sound terribly. She popped her head back above the water and Matt followed suit.

“Are you having fun?”

“Yeah! Terry showed me a cool magic spell.”

“Oh really? What was it?”

“It was a light spell! Like a magic flashlight!”

“A magic flashlight? That could come in handy. Will you show me sometime?”

“Yeah! Mr. Grayson says I’m learning magic really well, so I think I can do that one soon. Terry said it’s simple.”

“It is pretty simple, and he managed to refract some light just last week, so I’d say he’s on track to cast light in no time.” said Tim from his spot on the bench where he was putting his own swim gear on.

“That’s good. I’m glad you’re doing good, sweetie.”

Matt beamed.

Just then, Dick, Terry and Jason surfaced. Terry taking the time to spit a stream of water at Matt, who took the bait and darted over quicker than Mary could hope to achieve to initiate an underwater wrestling session with his older brother while the adults all laughed.

“Hi, Mary.” said Jason, swimming over for a greeting hug. “How’s land life?”

“Going as well as can be expected. Terry’s doing well in PT, he’s gunning to be done soon. Matt loves the little sunfish necklace you gave him, and I’m still talking to that lady from the physics department, so there might be hope for me yet.”

“Well, if you ever need someone to watch Matt for the night, feel free to just drop him off whenever.” said Dick with a slightly teasing smile.

“Oh please, we’ve barely gotten past the ‘staring at each other from across the lunchroom’ phase.”

“I just meant for like a simple date night! Or any night. Really, whenever you want some time off we’ll gladly look after him for you.”

“Thank you, Dick. He really likes spending time with you all.”

“We’re pretty cool uncles.”

“Keep telling yourself that.” said Tim as he waded up beside them.

“Hey! It’s not like you’re any better.”

“I never claimed to be.”

Dick’s coming retort was interrupted by a shouted “Hey, mom!” and a small body ramming into hers. Terry, from his spot behind Jason said something to the effect of “Wait up, twip!” as Matt looked up at her with the biggest most ‘I am up to something’ grin he could muster and said:

“Since Terry’s the Bat Mer, and I’m mer now too, can I be Robin?”

Mary felt her heart do something funny. She stared at her son, then remembered who was in the room with her and shot an accusatory glare at the three former Robins and one current Bat Mer in front of her, all of whom were either awkwardly avoiding her eye, or in Terry’s case, slowly sinking into the water.

“Not my idea.” squeaked Terry before dropping out of sight with a small splash. 

She turned her gaze back to the very much in trouble adult Wayne boys.

“I never said anything about it to him!” said Dick, hands thrown up in supplication, the two others nodding along eagerly.

She frowned. The Wayne family might be okay, but Mary had a feeling she would need to find different babysitters for the near future.

\--

****Bonus:****

“B, oh my  _ lord _ , B! B do you realize what this means?!” shouted Dick.

“What?” 

“You’re free! You’re free from Alfred’s curse!”

“Alfred cursed him?” asked a confused Terry.

“Alfred cursed him to have ten children just like him. And now with Matt, that makes ten! You’re a free mer, Bruce!”

Bruce rolled his eyes as his children erupted into laughter, Matt and Terry finding it funniest of all. Not a single shred of respect in his own house. 

Alfred would have loved them.

(((([link to this au's masterpost](https://theycallme-ook.tumblr.com/post/643487237164630016/owlady-merau-masterlist)))))

**Author's Note:**

> matt: can i be robin?!!  
> everyone else: :|


End file.
